The present invention relates to an improved method for the preparation of wrought sheet products such as tread plate from aluminum base alloys containing silicon and magnesium which possess high strength and high impact properties.
The preparation of sheet or plate products from aluminum base alloys is well known. Particularly, the preparation of aluminum tread plate has long been desirable for use in industrial, marine and transportation applications. Aluminum tread plate is generally a sheet or plate product produced with a raised pattern on its surface which provides a non-skid feature. The pattern is usually provided by an embossing operation performed in conjunction with the roll processing of the alloy. Because of its utility, tread plate is generally employed in situations involving substantial loading, and consequently a tread plate product must have sufficient properties to insure safe performance under various design loading conditions. The above properties must also be obtainable with a relative ease of manufacture which would make the preparation of aluminum tread plate commercially desirable.
Conventional processing of aluminum base alloys in this regard, particularly alloys of the 6000 Series containing magnesium and silicon, such as Alloy 6061, has required that the alloy be solution treated and quenched prior to aging to yield a product possessing the required strength levels in service. Solution heat treatment is undesirable because it is costly, time-consuming, requires special equipment and handling and often degrades the surface appearance of the product. In addition, undesirable distortion and residual stresses are developed which must be eliminated by additional processing treatments such as thermal flattening, light roll reductions and/or stretching.